A typical power drill has a motor and a drive spindle rotatably mounted in a housing, and a drilling chuck with a chuck body in which displaceable jaws are guided by a threaded connection formed between a threaded drive member and a threaded stem element.
A drilling chuck of the kind described above is disclosed in DE 10 2009 026 075 (U.S. application Ser. No. 13/302,037 filed 4 Mar. 2012). It has a housing, a tubular drive spindle extending forward along an axis from the housing, a drive motor in the housing and permanently connected to the spindle for rotating the spindle about the axis, and a chuck body carried on the spindle outside the housing. An internally threaded sleeve element is provided in the spindle, and a driver, sleeve, and holder carried on the chuck body form a plurality of angularly spaced angled guides receiving respective jaws axially rearwardly braced on the driver. A stem element on the driver is threaded into the sleeve element. A rod rotationally coupled to the one of the elements extends axially through the spindle so that relative rotation of the one element and the stem shifts the jaws in the guides. A coupling rotationally fixed to the rod is axially shiftable between a tightening position engaging the housing and a drilling position engaging the chuck body. Interfitting formations on the coupling, the housing, and the chuck body rotationally lock the one element to the rod and couple the rod to the housing in the tightening position and to the chuck body in the drilling position.
In the drilling configuration, the coupling rod is rotationally connected to the tubular drive spindle so that, in the tightening position that serves to displace the jaws, the coupling rod is decoupled from the tubular drive spindle and is rotationally connected to the housing. In doing so, the coupling rod and the threaded stem element are fixed with respect to the rotation of the tubular drive spindle driven by the motor. The tubular drive spindle is rotationally connected to the chuck body and to the jaw holder so that the threaded drive member is screwed in and out on rotation of the chuck body, and the jaws are therefore displaced by the motor of the power drill. This is a possible way of adjusting the jaws with the help of the power drill drive. In doing so however, it is difficult for a user to fit a drilling tool in the power drill between the jaws, as the chuck body, which is on the outside of the power drill and is driven by the power drill motor, rotates during the clamping process.